Advanced Materials Division, Korea Research Institute of Chemical Technology (KRICT) , Daejeon 305-600, Republic of Korea.
Chemical Convergence Materials Major, University of Science and Technology (UST) , Daejeon 305-350, Republic of Korea.
ACS Appl Mater Interfaces. 2016 May 25;8(20):12940-50. doi: 10.1021/acsami.6b01576. Epub 2016 May 13.
A series of small compound materials based on benzodithiophene (BDT) and diketopyrrolopyrrole (DPP) with three different alkyl side chains were synthesized and used for organic photovoltaics. These small compounds had different alkyl branches (i.e., 2-ethylhexyl (EH), 2-butyloctyl (BO), and 2-hexyldecyl (HD)) attached to DPP units. Thin films made of these compounds were characterized and their solar cell parameters were measured in order to systematically analyze influences of the different side chains of compounds on the film microstructure, molecular packing, and hence, charge-transport and recombination properties. The relatively shorter side chains in the small molecules enabled more ordered packing structures with higher crystallinities, which resulted in higher carrier mobilities and less recombination factors; the small molecule with the EH branches exhibited the best semiconducting properties with a power conversion efficiency of up to 5.54% in solar cell devices. Our study suggested that tuning the alkyl chain length of semiconducting molecules is a powerful strategy for achieving high performance of organic photovoltaics.
一系列基于苯并二噻吩（BDT）和二酮吡咯并吡咯（DPP）的小分子化合物，具有三种不同的烷基侧链，被合成并用于有机光伏。这些小分子化合物在 DPP 单元上具有不同的烷基支链（即 2-乙基己基（EH）、2-丁基辛基（BO）和 2-己基癸基（HD））。这些化合物的薄膜进行了表征，并测量了它们的太阳能电池参数，以便系统地分析化合物不同侧链对薄膜微结构、分子堆积以及电荷输运和复合性质的影响。小分子中较短的侧链可以形成更有序的堆积结构，具有更高的结晶度，从而导致更高的载流子迁移率和更少的复合因素；具有 EH 支链的小分子表现出最好的半导体性能，在太阳能电池器件中达到了高达 5.54%的功率转换效率。我们的研究表明，调整半导体分子的烷基链长度是实现有机光伏高性能的一种有效策略。
